Air conditioners are apparatuses for cooling/heating or purifying air in an indoor space in order to provide more comfortable indoor environment to a user.
Such an air conditioner may be classified into a split type air conditioner in which indoor and outdoor units are separated from each other and an integral type air conditioner in which indoor and outdoor units are integrally coupled to each other as a single unit. Air conditioners may also be classified into single type air conditioners having capacity that is capable of operating one indoor unit so as to be used in narrow spaces, middle and large sized air conditioners having very large capacity so as to be used in companies or restaurants, and multi type air conditioners having capacity that is capable of sufficiently operating a plurality of indoor units according to the capacity thereof.
Here, such a split type air conditioner includes an indoor unit installed in an indoor space to supply hot wind or cold wind into a space to be air-conditioned and an outdoor unit in which compression and expansion are performed for performing a sufficient heat-exchanging operation in the indoor unit.
Also, the air conditioner may be classified into an electric heat pump (EHP) type air conditioner and a gas heat pump (GHP) type air conditioner according to power sources for driving a compressor. The EHP type air conditioner uses electricity as a power source for the compressor, and the GHP type air conditioner uses a fuel such as an LNG or LPG as a power source for the compressor. In the GHP type air conditioner, an engine operates through fuel combustion to provide an output of a compressor motor.
A prior art document relating to the GHP type air conditioner: Patent Application No. 10-2012-0016202
A prior art document relating to the EHP type air conditioner: Patent Application No. 10-2003-0077857
In the EHP type air conditioner according to the related art, supplied current may be adjusted to easily control the compressor. Thus, the EHP type air conditioner may be adequate for response to a partial load and has high energy efficiency. However, the EHP type air conditioner may have a limitation in that frost is attached to an outdoor heat exchanger when low-temperature heating is performed.
On the other hand, the GHP type air conditioner may have an advantage in that waste heat of the engine is used to improve defrosting performance. However, the GHP type air conditioner may have low engine efficiency due to heat losses.